Characterization of dextran produced by the food-related strain Weissella cibaria C43-11 and of the relevant dex-transucrase gene

A metabolic feature of lactic acid bacteria (LAB) is the production of exopolysaccharides(EPSs), which have technological and functional properties of interest to the food sector. The presentstudy focused on the characterization of the Weissella cibaria strain C43-11, a high EPS producer inthe presence of sucrose, in comparison with a low-producing strain (C2-32), and on possible geneticregulatory elements responsible for the modulation of dextransucrase (dsr) genes expression. NMRanalysis of the polymeric material produced by the C43-11 strain indicated the presence of dextranconsisting mainly of a linear scaffold formed by -(1-6) glycosidic linkages and a smaller amountsof branches derived from -(1-2), -(1-3), and -(1-4) linkages. Molecular analysis of the dsr genesand the putative transcriptional promoters of the two strains showed differences in their regulatoryregions. Such variations may have a role in the modulation of dsr expression levels in the presence ofsucrose. The strong upregulation of the dsr gene in the C43-11 strain resulted in a high accumulationof EPS. This is the first report showing differences in the regulatory elements of the dsr gene in W.cibaria and indicates a new perspective of investigation to identify the regulatory mechanism ofEPS production.